An example of such seal is a duct seal, where a seal is needed between a cable, for example, and a wall, or bulkhead, duct through which it passes, to prevent moisture or other contaminants travelling along the duct. A further type of duct seal is one in which a duct designed to carry a cable is empty, and it is necessary to block off the duct completely until the cable is installed.
The reason that a seal (rather than an adhesive bond of no significant thickness) is required in the first instance is a disparity in size or shape between the aperture surface and that of the elongate substrate or substrates. For example, a duct may be from several millimeters to several centimeters greater than the cable it carries.
Such seals have usually been formed by the use of a conformable sealing member, for example an O-ring, or the use of a mass of a sealant or hot-melt adhesive. Whilst these seals in general work in a satisfactory manner, problems sometimes occur. For example, by their nature, conformable sealing members have a low modulus and, especially where they are used to fill large voids, have a tendency to creep over extended periods of time. Leak paths may result which permit, for example, ingress of moisture to a sensitive area.
It has been proposed, in British Specification No. 1,485,621, to pump foamable material into a duct to fill the space between the cable or cables and the duct. Since, however, the foamable material is not in any way constrained against penetration of the duct, much material may be consumed before the duct is closed, with resulting waste both of time and material, and leak paths that interface between the foamed material and the duct are possible and difficult to detect.
There accordingly remains a need for a method and device to seal ducts and similar apertures, whether carrying an elongate substrate or not.